The present invention relates to electromagnetic shielding and, more particularly, to an electronic device having an electromagnetic gasket located between a chassis and an electronic component located within the electronic device.
Many electronic devices, such as computers, are made from a plurality of various electronic components, such as printed circuit boards, located within a single housing. The printed circuit boards are typically electrically and mechanically connected to a backplane or motherboard that is located within the housing. Many of the circuit boards are removable and are used to connect peripheral devices to the electronic device. For example peripheral component interconnect (PCI) circuit boards or cards are often used to connect computer peripheral devices to a computer, e.g., a computer motherboard.
Developments in electronics have increased the capabilities of many electronic devices and decreased the sizes of these electronic devices. As the capabilities of the electronic devices have increased, the number of electronic components, such as PCI boards, required to be located within the electronic devices has generally increased. The reduced sizes of the electronic devices coupled with the increased number of electronic components located within the electronic devices have caused the density of electronic components located within the electronic devices to increase.
The capabilities of the electronic components have increased to meet the increased capabilities of the electronic devices. The increased capabilities of the electronic components typically cause them to operate at higher temperatures. The above-described higher density of electronic components within the electronic devices causes a higher heat density within the electronic devices in the proximity of the electronic components. Excessive heat generally has detrimental affects on the electronic components.
In the situation where the electronic device is a computer, the electronic components described above are often PCI boards. Many of the PCI boards are mounted to the motherboard of the computer so that they extend perpendicular from the motherboard and are, thus, parallel to each other. This arrangement of PCI boards provides for a high density of PCI boards within a small computer housing, however, it typically does not allow for the free flow of cooling air within the housing. The PCI boards generally do not perform reliably unless they are maintained relatively cool during their operation. Accordingly, the lack of free flowing air causes a trade off between the capabilities and the sizes of computers. For example, the capabilities of computers may increase, however, the sizes of the housings has to increase in order to provide the necessary airflow.
Another drawback of the improved capabilities of the electronic components is that many of the electronic components emit and/or are susceptible to electromagnetic interference (EMI). Accordingly, many of the electronic devices are required to have extensive EMI shielding to shield the electronic components. The EMI shielding requirements present problems with PCI boards because the PCI boards provide an interface to external peripheral components and are, thus, required to be associated with openings in the electronic devices. These openings are generally detrimental to the EMI requirements of the electronic devices. Some PCI boards have a conductive bulkhead that covers the opening in the electronic devices, which serves to attenuate EMI. These bulkheads, however, do not sufficiently attenuate EMI for many high performance PCI boards because they cannot be grounded properly.
As more PCI boards are used in electronic devices, more openings have to be placed in the electronic devices to accommodate the PCI boards. More openings also have to be provided to accommodate the increased airflow required to cool the PCI boards. These openings degrade the structural integrity of the electronic devices in addition to degrading the EMI shielding of the electronic devices.
Therefore, a need exists for an electronic device having improved EMI shielding and ventilation, but which does not have reduced structural integrity.
The present invention is directed toward an electronic device having improved electromagnetic interference (EMI) shielding, ventilation, and structural integrity. The electronic device may have a chassis for supporting electronic components, such as a peripheral component interconnect (PCI) boards, and a mother board to which the electronic components are attached. The chassis may comprise at least a first member and a second member extending between a first panel and a second panel. The first and second members may have a plurality of ventilation holes formed therein. A space may exist between the first member and the second member and may be occupied by a bulkhead portion of a PCI board.
A conductive sheet (EMI gasket) having a first portion and a second portion may be placed adjacent the first member and the second member. The first portion and the second portion may have a plurality of holes formed therein that correspond to the plurality of ventilation holes formed in the first and second chassis members. The conductive sheet first portion is located adjacent the first member and the conductive sheet second portion is located adjacent the second member. The conductive sheet is positioned so that the holes in the conductive sheet are aligned with the ventilation holes in the chassis members. A plurality of tabs are formed into the conductive sheet and serve to improve the electrical contact between the chassis and the PCI boards by causing the conductive sheet to have a spring force acting between the chassis and the PCI boards.